1. Field of the Invention
The present invention relates to foil journal bearings, and more particularly to a foil journal bearing utilizing semi-active dampers which improves the stiffness of the bearing against rotational shaft-supported load and the vibration suppressing capability of the bearing.
2. Description of the Prior Art
In general, a foil journal bearing employs air as lubricating material instead of lubricating oil, and therefore it is generally suitable for a clean mechanical system. Such a foil journal bearing has a relatively wide area for supporting a rotating member in comparison with other bearings, thus having high reliability. Accordingly, the foil journal bearing can be utilized as a supporting bearing for small, general aerial gas turbine engines, turbo expanders, various aerospace auxiliary power units, land transportation means, vapor cycle centrifugal compressors, and various commercial air compressors.
The foil journal bearing should be designed to have load-carrying capacity and stability, and withstand wear due to unstable contact between a shaft and a bearing during its starting and stopping.
FIG. 1 shows a sectional view of a conventional multi-leaf type foil journal bearing. A plurality of axial grooves 12a are formed on the inner surface of a bearing housing 12 while being spaced apart from one another. A plurality of the multi-leaf foils 14 are arranged into the axial grooves 12a, and support a shaft 10. The conventional multi-leaf foil journal bearing shown as FIG. 1 can increase stiffness as being increased the thickness of the multi-leaf foil 14. However, the conventional multi-leaf type foil journal bearing is problematic in that the thickness of the foil is restricted and the life span of the bearing is restricted due to wear between the shaft 10 and the foils 14. The vibration of the shaft 10 is controlled by only a factor of the multi-leaf foil 14, for example, the thickness or the number of the foils, so that it is difficult to control the vibration of the shaft 10.
FIG. 2 illustrates a sectional view of a bump foil journal bearing in which a top foil 16 and a bump foil 18 are positioned on the inner surface of a bearing housing 12 and support a shaft 10 thereon. The bump foil journal bearing can increase load-carrying capacity by the great stiffness of the bump foil 18. However, gas in the bump foil 18 leaks in its axial direction, thereby being reduced the damping capacity of the bump bearing. In addition, the conventional bump foil journal bearing is further problematic in that it is difficult to design and form the bump foil 18.
The main object of the present invention is to provide a foil journal bearing utilizing semi-active dampers, which improves load-carrying capacity and stability to be high by increasing stiffness and damping capacity.
Another object of the present invention is to provide a semi-active damper foil journal bearing which reduces the damping vibration and instability of the bearing by gas in a space between damper pin and a dimple of the bearing housing and/or which increase the stiffness by the spring under the damper pin when a shaft rotates fast.
In order to accomplish the above object, the present invention provides a foil journal bearing which is provided at an interior surface of the bearing housing with a plurality of foils or one foil for supporting a shaft wherein the bearing comprising a plurality of dampers embedded in an inside portion of its bearing housing while coming into contact with and supporting the plurality of foils or the one foil to increase stiffness and damping capacity of the bearing during rotation of said shaft, wherein each of said dampers is comprised of a damper pin inserted into one of dimples formed on the interior surface of the bearing housing and an elastic spring interposed between a bottom of the damper pin and a bottom of the dimple.
In order to accomplish the above object, the present invention provides a foil journal bearing for supporting a shaft, wherein the bearing comprising a plurality of foils or one foil at an interior surface of the foil journal bearing housing, and a plurality of dampers embedded in the interior surface of the foil journal bearing housing while coming into contact with and supporting the foils or the one foil to increase stiffness and damping capacity of the bearing during rotation of said shaft.